U.S. patent application number 10/117851 was filed with the patent office on 2003-10-09 for acoustic based pointing device.
This patent application is currently assigned to Koninklijke Philips Electronics N.V.. Invention is credited to Colmenarez, Antonio, Gutta, Srinivas, Trajkovic, Miroslav.
Application Number | 20030189545 10/117851 |
Document ID | / |
Family ID | 28674295 |
Filed Date | 2003-10-09 |
United States Patent
Application |
20030189545 |
Kind Code |
A1 |
Trajkovic, Miroslav ; et
al. |
October 9, 2003 |
Acoustic based pointing device
Abstract
An acoustic based pointing device and a system and method for
using the pointing device to move a cursor on a display screen of a
display device. The pointing device comprises an acoustic source
that generates and propagates an acoustic signal that is detected
by four microphones M.sub.1, M.sub.2, M.sub.3, and M.sub.4 and is
then converted into corresponding periodic electrical signals
S.sub.1, S.sub.2, S.sub.3, and S.sub.4. The position vector P.sub.0
of the acoustic source is calculated by solving triangulation
equations that depend on phase-shift time delays between S.sub.1
and S.sub.j for j=1, 2, and 3. A position vector P.sub.C is
calculated from P.sub.0 using a scale vector that relates a change
in position of the cursor to a change in position of the acoustic
source. Then the cursor is moved to a position P.sub.C associated
with the position vector P.sub.C.
Inventors: |
Trajkovic, Miroslav;
(Ossining, NY) ; Colmenarez, Antonio; (Maracaibo,
VE) ; Gutta, Srinivas; (Yorktown Heights,
NY) |
Correspondence
Address: |
PHILIPS INTELLECTUAL PROPERTY & STANDARDS
P.O. BOX 3001
BRIARCLIFF MANOR
NY
10510
US
|
Assignee: |
Koninklijke Philips Electronics
N.V.
|
Family ID: |
28674295 |
Appl. No.: |
10/117851 |
Filed: |
April 8, 2002 |
Current U.S.
Class: |
345/156 |
Current CPC
Class: |
G06F 3/0433
20130101 |
Class at
Publication: |
345/156 |
International
Class: |
G09G 005/00 |
Claims
What is claimed is:
1. A method for moving a cursor on a display screen, comprising:
providing a display device having the display screen; providing
four microphones M.sub.1, M.sub.2, M.sub.3, and M.sub.4 at fixed
positions such that no three of M.sub.1, M.sub.2, M.sub.3, and
M.sub.4 are colinear; providing a wireless pointing device having
an acoustic source; moving the pointing device such that the
acoustic source is moved to a position P.sub.0 having an associated
position vector P.sub.0, wherein P.sub.0 is yet to be calculated;
propagating an acoustic signal from the acoustic source; detecting
the acoustic signal at microphone M.sub.i, for i=1, 2, 3, and 4;
converting the acoustic signal detected at microphone M.sub.i to a
periodic electrical signal S.sub.i, for i=1, 2, 3, and 4;
calculating P.sub.0 by solving triangulation equations that
comprise a dependence on a phase-shift time delay between S.sub.1
and S.sub.j, for j=2, 3, and 4; computing a position vector P.sub.C
for the cursor, wherein P.sub.C depends on: P.sub.0, a scale vector
A, and a shape function of the display screen; and moving the
cursor to a position P.sub.C associated with the position vector
P.sub.C.
2. The method of claim 1, wherein the display screen is planar.
3. The method of claim 1, wherein the display screen is
non-planar.
4. The method of claim 1, wherein the four microphones are within
or attached to the display device.
5. The method of claim 1, wherein the cursor is electrically
coupled to a computing system, wherein S.sub.1, S.sub.2, S.sub.3,
and S.sub.4 are each electrically coupled to the computing system,
wherein solving the triangulation equations for P.sub.0 is
implemented by the computing system, and wherein computing P.sub.C
is implemented by the computing system.
6. The method of claim 5, wherein the computing system is within or
attached to the display device, and wherein the four microphones
are within or attached to the display device.
7. The method of claim 5, wherein the computing system includes at
least one semiconductor chip, and wherein solving the triangulation
equations and computing P.sub.C are hardware-encoded within the at
least one semiconductor chip.
8. The method of claim 5, wherein the computing system includes a
processor, memory, and software, wherein the software is stored in
the memory, and wherein solving the triangulation equations and
computing P.sub.C are implemented through executing the software by
the processor.
9. The method of claim 1, wherein the pointing device comprises a
mouse.
10. The method of claim 1, wherein the display device comprises a
television.
11. The method of claim 1, wherein the display device comprises a
computer monitor.
12. The method of claim 1, wherein the acoustic signal comprises a
plurality of frequency components.
13. The method of claim 12, wherein each frequency component has a
frequency of at least about 20 kHz.
14. The method of claim 12, further comprising filtering the
electrical signal S.sub.i to remove from S.sub.i all frequency
components except the plurality of frequency components, for i=1,
2, 3, and 4.
15. The method of claim 1, wherein the acoustic signal comprises at
least three frequency components.
16. A system for moving a cursor on a display screen, comprising: a
display device having the display screen; four microphones M.sub.1,
M.sub.2, M.sub.3, and M.sub.4 at fixed positions such that no three
of M.sub.1, M.sub.2, M.sub.3, and M.sub.4 are colinear; a wireless
pointing device having an acoustic source, wherein the acoustic
source is located at a position P.sub.0 having an associated
position vector P.sub.0, wherein the acoustic source is adapted to
generate and propagate an acoustic signal, wherein the microphone
M.sub.i is adapted to detect the acoustic signal, and wherein the
acoustic signal detected at the microphone M.sub.i is adapted to be
converted to a periodic electrical signal S.sub.i, for i=1, 2, 3,
and 4; a computing system to which the cursor, S.sub.1, S.sub.2,
S.sub.3, and S.sub.4 are each electrically coupled, wherein the
computing system is adapted to calculate P.sub.0 by solving
triangulation equations that comprise a dependence on a phase-shift
time delay between S.sub.1 and S.sub.j, for j=2, 3, and 4, and
wherein the computing system is adapted to compute a position
vector P.sub.C for the cursor such that P.sub.C depends on:
P.sub.0, a scale vector A, and a shape function of the display
screen; and means for moving the cursor to a position P.sub.C
associated with the position vector P.sub.C.
17. The system of claim 16, wherein the display screen is
planar.
18. The system of claim 16, wherein the display screen is
non-planar.
19. The system of claim 16, wherein the four microphones are within
or attached to, the display device
20. The system of claim 16 wherein the computing system is within
or attached to the display device, and wherein the four microphones
are within or attached to the display device.
21. The system of claim 16, wherein the computing system includes
at least one semiconductor chip, and wherein solving the
triangulation equations and computing P.sub.C are hardware-encoded
within the at least one semiconductor chip.
22. The system of claim 16, wherein the computing system includes a
processor, memory, and software, wherein the software is stored in
the memory, and wherein solving the triangulation equations and
computing P.sub.C are implemented through executing the software by
the processor.
23. The system of claim 16, wherein the pointing device comprises a
mouse.
24. The system of claim 16, wherein the display device comprises a
television.
25. The system of claim 16, wherein the display device comprises a
computer monitor.
26. The system of claim 16, wherein the acoustic signal comprises a
plurality of frequency components.
27. The system of claim 26, wherein each frequency component has a
frequency of at least about 20 kHz.
28. The system of claim 26, further comprising a filter adapted to
remove from the electrical signal S.sub.i all frequency components
except the plurality of frequency components, for i=1, 2, 3, and
4.
29. The system of claim 16, wherein the acoustic signal comprises
at least three frequency components.
30. A pointing device, said pointing device being wireless and
comprising an acoustic source at a position P.sub.0 having an
associated position vector P.sub.0: wherein the acoustic source is
adapted to generate and propagate an acoustic signal that can be
detected by each of four microphones M.sub.1, M.sub.2, M.sub.3, and
M.sub.4 at fixed positions such that no three of M.sub.1, M.sub.2,
M.sub.3, and M.sub.4 are colinear; wherein the acoustic signal at
the microphone M.sub.i is adapted to be converted to a periodic
electrical signal S.sub.i that is coupled to a computing system,
for i=1, 2, 3, and 4; wherein the computing system is adapted to
calculate P.sub.0 by solving triangulation equations that comprise
a dependence on a phase-shift time delay between S.sub.1 and
S.sub.j, for j=2, 3, and 4; and wherein the computing system is
adapted to compute a position vector P.sub.C for a cursor on a
display screen such that P.sub.C depends on: P.sub.0, a scale
vector A, and a shape function of the display screen.
31. The pointing device of claim 30, wherein the display screen is
planar.
32. The pointing device of claim 30, wherein the display screen is
non-planar.
33. The pointing device of claim 30, wherein the four microphones
are within or attached to the display device.
34. The pointing device of claim 30 wherein the computing system is
within or attached to the display device, and wherein the four
microphones are within or attached to the display device.
35. The pointing device of claim 30, wherein the computing system
includes at least one semiconductor chip, and wherein solving the
triangulation equations and computing P.sub.C are hardware-encoded
within the at least one semiconductor chip.
36. The pointing device of claim 30, wherein the computing system
includes a processor, memory, and software, wherein the software is
stored in the memory, and wherein solving the triangulation
equations and computing P.sub.C are implemented through executing
the software by the processor.
37. The pointing device of claim 30, wherein the pointing device
comprises a mouse.
38. The pointing device of claim 30, wherein the display device
comprises a television.
39. The pointing device of claim 30, wherein the display device
comprises a computer monitor.
40. The pointing device of claim 30, wherein the acoustic signal
comprises a plurality of frequency components.
41. The pointing device of claim 40, wherein each frequency
component has a frequency of at least about 20 kHz.
42. The pointing device of claim 30, wherein the acoustic signal
comprises at least three frequency components.
43. The pointing device of claim 42, wherein each frequency
component has a frequency of at least about 20 kHz.
Description
BACKGROUND OF THE INVENTION
[0001] 1. Technical Field
[0002] The present invention relates generally to a system and
method for moving a cursor on a display screen, and more
particularly to use of an acoustic based pointing device for moving
the cursor on the display screen.
[0003] 2. Related Art
[0004] A commercially available wireless pointing device exploits
the gyroscopic effect. Consequently, such commercially available
wireless pointing devices rely on the rotation of the pointing
device which makes these pointing devices very unintuitive and
inhibits the ability to track the positions of these pointing
devices. Additionally, these pointing devices are fundamentally
heavy since they need a large mass in order to exploit conservation
of angular momentum.
[0005] Accordingly, there is a need for wireless pointing device
that eliminate the aforementioned disadvantages of commercial
wireless pointing devices that are currently available.
SUMMARY OF THE INVENTION
[0006] A first embodiment of the present invention provides a
method for moving a cursor on a display screen, comprising:
[0007] providing a display device having the display screen;
[0008] providing four microphones M.sub.1, M.sub.2, M.sub.3, and
M.sub.4 at fixed positions such that no three of M.sub.1, M.sub.2,
M.sub.3, and M.sub.4 are colinear;
[0009] providing a wireless pointing device having an acoustic
source;
[0010] moving the pointing device such that the acoustic source is
moved to a position P.sub.0 having an associated position vector
P.sub.0, wherein P.sub.0 is yet to be calculated;
[0011] propagating an acoustic signal from the acoustic source;
[0012] detecting the acoustic signal at microphone M.sub.i, for
i=1, 2, 3, and 4;
[0013] converting the acoustic signal detected at microphone
M.sub.i to a periodic electrical signal S.sub.i, for i=1, 2, 3, and
4;
[0014] calculating P.sub.0 by solving triangulation equations that
comprise a dependence on a phase-shift time delay between S.sub.1
and S.sub.j, for j=2, 3, and 4;
[0015] computing a position vector P.sub.C for the cursor, wherein
P.sub.C depends on: P.sub.0, a scale vector A, and a shape function
of the display screen; and
[0016] moving the cursor to a position P.sub.C associated with the
position vector P.sub.C.
[0017] A second embodiment of the present invention provides a
system for moving a cursor on a display screen, comprising:
[0018] a display device having the display screen;
[0019] four microphones M.sub.1, M.sub.2, M.sub.3, and M.sub.4 at
fixed positions such that no three of M.sub.1, M.sub.2, M.sub.3,
and M.sub.4 are colinear;
[0020] a wireless pointing device having an acoustic source,
wherein the acoustic source is located at a position P.sub.0 having
an associated position vector P.sub.0, wherein the acoustic source
is adapted to generate and propagate an acoustic signal, wherein
the microphone M.sub.i is adapted to detect the acoustic signal,
and wherein the acoustic signal detected at the microphone M.sub.i
is adapted to be converted to a periodic electrical signal S.sub.i,
for i=1, 2, 3, and 4;
[0021] a computing system to which the cursor, S.sub.1, S.sub.2,
S.sub.3, and S.sub.4 are each electrically coupled, wherein the
computing system is adapted to calculate P.sub.0 by solving
triangulation equations that comprise a dependence on a phase-shift
time delay between S.sub.1 and S.sub.j, for j=2, 3, and 4, and
wherein the computing system is adapted to compute a position
vector P.sub.C for the cursor such that P.sub.C depends on:
P.sub.0, a scale vector A, and a shape function of the display
screen; and
[0022] means for moving the cursor to a position P.sub.C associated
with the position vector P.sub.C.
[0023] A third embodiment of the present invention provides a
pointing device, said pointing device being wireless and comprising
an acoustic source at a position P.sub.0 having an associated
position vector P.sub.0:
[0024] wherein the acoustic source is adapted to generate and
propagate an acoustic signal that can be detected by each of four
microphones M.sub.1, M.sub.2, M.sub.3, and M.sub.4 at fixed
positions such that no three of M.sub.1, M.sub.2, M.sub.3, and
M.sub.4 are colinear;
[0025] wherein the acoustic signal at the microphone M.sub.i is
adapted to be converted to a periodic electrical signal S.sub.i
that is coupled to a computing system, for i=1, 2, 3, and 4;
[0026] wherein the computing system is adapted to calculate P.sub.0
by solving triangulation equations that comprise a dependence on a
phase-shift time delay between S.sub.1 and S.sub.j, for j=2, 3, and
4; and
[0027] wherein the computing system is adapted to compute a
position vector P.sub.C for a cursor on a display screen such that
P.sub.C depends on: P.sub.0, a scale vector A, and a shape function
of the display screen.
[0028] The present invention provides a pointing device that
eliminates the disadvantages associated with commercial wireless
pointing devices that are currently available. For example, the
acoustic based pointing device of the present invention is or may
be: wireless, accurate, lightweight, hand held, and easily tracked
with respect to its motions and spatial positions. Additionally,
the user is able to use the pointing device of the present
invention in a way that is analogous to use of a conventional
computer mouse with the added advantage that the pointing device of
the present invention is wireless.
BRIEF DESCRIPTION OF THE DRAWINGS
[0029] FIG. 1 depicts a three-dimensional view of a system for
moving a cursor on a display screen of a display device, in
accordance with embodiments of the present invention.
DETAILED DESCRIPTION OF THE INVENTION
[0030] FIG. 1 illustrates a three-dimensional view of a system 10
for moving a cursor 40 on a display screen 14 of a display device
12, in accordance with embodiments of the present invention. FIG. 1
shows a three-dimensional Cartesian coordinate system having three
mutually orthogonal axes identified as X, Y, and Z axes having a
coordinate origin at the point 50. The Z axis is oriented in a
"depth" direction into or out of the display screen 14 as perceived
by a viewer who is viewing the display screen 14. The X and Y axes
define a plane, namely the X-Y plane, such that the Z axis is
normal to the X-Y plane If the display screen 14 has a planar
shape, then the display screen 14 is parallel to the X-Y plane. The
present invention accounts for the shape of the display screen 14,
regardless of whether the display screen 14 is planar or
non-planar. Any vector shown in FIG. 1 is a three dimensional
vector having components along the X, Y, and Z axes. The system 10
comprises the display device 12, a pointing device 20, four
microphones denoted as M.sub.1, M.sub.2, M.sub.3, and M.sub.4, and
a computing system 30.
[0031] The display device 12 is capable of receiving an image in
electronic form and displaying the image visually on the display
screen 14. The display device 12 may comprise, inter alia, a
television, a computer monitor, etc.
[0032] The pointing device 20 is capable of controlling motion of a
cursor 40 on the display screen 14 of the display device 12. The
pointing device 20 may comprise, inter alia, a mouse. The pointing
device 20 includes an acoustic source 22 that is adapted to
continuously generate and propagate an acoustic signal 28 (i.e.,
longitudinal acoustic waves) through the ambient atmosphere. The
acoustic source 22 has an associated wave front 26. The acoustic
source 22 is at a position P.sub.0 with an associated position
vector P.sub.0. FIG. 1 also shows the acoustic source 22 at a
reference position P.sub.0,REF REF with an associated position
vector P.sub.0,REF. Vectors P.sub.0 and P.sub.0,REF each have a
component along each of the X, Y, and Z axes.
[0033] The cursor 40 is at a position Pc having an associated
position vector P.sub.C, as measured from the coordinate origin 50.
The position Pc may be on the display screen 14, or "behind" the
display screen 14 to simulate an apparent depth of the cursor 40
relative to the display screen 14. For the case of no apparent
depth, Pc and P.sub.C trace a path on the surface of the display
screen 14 as the cursor 40 moves. FIG. 1 also shows the cursor 40
at a position that has an associated reference position vector
P.sub.C,REF. For simplicity, P.sub.C,REF may be chosen to be on the
display screen 14. Vectors P.sub.C and P.sub.C,REF each have a
component along each of the X, Y, and Z axes. P.sub.C,REF
corresponds to P.sub.0,REF (i.e., the cursor 40 is at the reference
screen position vector P.sub.C,REF when the acoustic source 22 is
at the reference position P.sub.0,REF).
[0034] The microphones M.sub.1, M.sub.2, M.sub.3, and M.sub.4 are
at positions P.sub.1, P.sub.2, P.sub.3, and P.sub.4 with associated
position vectors P.sub.1, P.sub.2, P.sub.3, and P.sub.4,
respectively. P.sub.1, P.sub.2, P.sub.3, and P.sub.4 each have a
component along each of the X, Y, and Z axes. While FIG. 1 shows
the microphones M.sub.1, M.sub.2, M.sub.3, and M.sub.4 to be
positioned in a particular geometric arrangement on a surface of
the display device 12, the microphones M.sub.1, M.sub.2, M.sub.3,
and M.sub.4 may be in any geometric arrangement relative to one
another such that no three of M.sub.1, M.sub.2, M.sub.3, and
M.sub.4 are colinear. Each of the microphones M.sub.1, M.sub.2,
M.sub.3, and M.sub.4 may be independently located on, within, or
outside of the display device 12.
[0035] The computing system 30 may comprise at least one
semiconductor chip that has hardware-encoded algorithms.
Alternatively, the computing system 30 may comprise a memory and
processor (e.g., a computer) for storing and executing software,
respectively. The computing system 30 is electrically coupled to
the cursor 40 through an electrical path 32 (e.g., electrical
wiring), which enables the computing system 30 to control the
motion and position of the cursor 40. While FIG. 1 shows the
computing system 30 to be located within the display device 12, the
computing system 30 could be located on, within, or outside of the
display device 12.
[0036] The acoustic source 22 continuously generates and propagates
the acoustic signal 28. The microphones M.sub.1, M.sub.2, M.sub.3,
and M.sub.4 are each adapted to detect the acoustic signal 28. The
acoustic signal 28 detected at the microphones M.sub.i is adapted
to be converted to a periodic electrical signal (e.g., an
alternating current sinusoidal signal) S.sub.i for i=1, 2, 3, and
4. Each electrical signal of the electrical signals S.sub.1,
S.sub.2, S.sub.3, and S.sub.4 is phase-shifted with respect to
another signal of the electrical signals S.sub.1, S.sub.2, S.sub.3,
and S.sub.4, as a consequence of the difference in magnitude of the
distance between the acoustic source 22 at the position P.sub.0 and
each of the positions P.sub.1, P.sub.2, P.sub.3, and P.sub.4 of the
microphones M.sub.1, M.sub.2, M.sub.3, and M.sub.4,
respectively.
[0037] The electrical signals S.sub.1, S.sub.2, S.sub.3, and
S.sub.4 so generated are each electrically coupled to the computing
system 30. If the pointing device 20 has been moved to the position
P.sub.0 corresponding to the associated position vector P.sub.0,
then the cursor 44 must be moved to its position P.sub.C
corresponding to its associated position vector P.sub.C. The
computing system 30 is adapted to calculate the position vector
P.sub.0 of the acoustic source 22, by processing the electrical
signals S.sub.1, S.sub.2; S.sub.3, and S.sub.4. For example, the
computing system 30 may calculate P.sub.0 by solving the
triangulation equations
.vertline.P.sub.1-P.sub.0.vertline.-.vertline.P.sub.j-P.sub.0.vertline.=C.-
DELTA.T.sub.1j
[0038] for j=2, 3, and 4. .DELTA.T.sub.ij is defined as a
phase-shift time delay between electrical signals S.sub.1 and
S.sub.j, for: i=1, 2, 3, 4; j=1, 2, 3, 4; and i.noteq.j. C is the
speed of the acoustic signal 28 in the ambient atmosphere.
Equations (1) comprise three equations corresponding to j=2, 3, and
4, which may be solved simultaneously for the three unknowns
P.sub.0X, P.sub.0Y, and P.sub.0Z by any computational method known
to a person of ordinary skill in the art of numerical analysis and
computation. The unknowns P.sub.0X, P.sub.0Y, and P.sub.0Z are the
components of the position vector P.sub.0 along the X, Y, and Z
axes, respectively. Note that the scope of the present invention
includes any mathematically equivalent form of Equations (1), and
includes any other applicable triangulation technique known to a
person of ordinary skill in the art. If the computing system 30
comprises at least one semiconductor chip, then the solution to
Equations (1) may be hardware-encoded within the at least one
semiconductor chip. If the computing system 30 comprises a memory
and processor (e.g., a computer), then a solution algorithm for
Equations (1) may be stored as software (e.g., as a computer
program) in said memory and said software may be executed by said
processor.
[0039] Following calculation of the position vector P.sub.0 of the
acoustic source 22, the vector position P.sub.C of the cursor 44 is
calculated via the equations
P.sub.CX=P.sub.CX,REF+A.sub.X(P.sub.0X-P.sub.0X,REF) (2A)
P.sub.CY=P.sub.CY,REF+A.sub.Y(P.sub.0Y-P.sub.0Y,REF) (2B)
P.sub.CZ=P.sub.CZ,REF+A.sub.Z(P.sub.0Z-P.sub.0Z,REF)+(Z.sub.S(P.sub.CXP.su-
b.CY)-P.sub.CZ,REF) (2C)
[0040] P.sub.CX, P.sub.CY, and P.sub.CZ are the components of
P.sub.C along the X, Y, and Z axes, respectively. P.sub.CX,REF and
P.sub.CY,REF and P.sub.CZ,REF are the components of P.sub.C,REF
along the X, Y, and Z axes, respectively. P.sub.0X,REF and
P.sub.0Y,REF and P.sub.0Z,REF are the components of P.sub.0,REF
along the X, Y, and Z axes, respectively. P.sub.CZ,REF is assumed
to describe a reference coordinate of the cursor 44 on the surface
of the display screen 14. Z.sub.S(P.sub.CX,P.sub.CY) is the Z
coordinate of the cursor 44 on the surface of the display screen 14
at P.sub.CX and P.sub.CY (i.e., at the X and Y coordinates of the
cursor 44). Generally, Z.sub.S(X,Y) is the Z coordinate of the
surface of the display screen 14 as a function of X and Y. Thus,
Z.sub.S(X,Y) is a "shape function" the display screen 14. If the
display screen 14 is planar, then
Z.sub.S(P.sub.CX,P.sub.CY)=P.sub.CZ,REF (i.e., the shape function
is "flat") and Equation (2C) for P.sub.CZ simplifies to
P.sub.CZ=C.sub.CZ,REF+A.sub.Z(P.sub.0Z-P.sub.0Z,REF), which is of
the same form as Equations (2A) and (2B) for P.sub.CX and P.sub.CY,
respectively. However, the display screen 14 may be non-planar such
that Z.sub.S(X,Y) is not constant and
Z.sub.S(P.sub.CX,P.sub.CY).noteq.P.sub.C- Z,REF ((i.e., the shape
function is "not flat"). The scope of the present invention
includes any mathematically equivalent form of Equations (2A),
(2B), and (2C).
[0041] Following calculation of P.sub.C, the cursor 44 is moved to
the position P.sub.C in response to movement of the pointing device
20 to the position P.sub.0. The physical motion of the cursor 44 to
the position P.sub.C is accomplished by using any electronics and
hardware that is known to a person of ordinary skill in the art.
The quantities A.sub.X, A.sub.Y, and A.sub.Z are components of a
scale vector A and are scale factors in the X, Y, and Z directions,
respectively; i.e., the scale vector A governs the magnitude of the
movement of the cursor 44 in response to the corresponding movement
of the pointing device 20. In accordance with Equations (2A) and
(2B), A.sub.X and A.sub.Y govern motion of the cursor 44 in the X-Y
plane. In accordance with Equation (2C),
(Z.sub.S(P.sub.CX,P.sub.CY)-P.sub.CZ,REF) is the change in the Z
coordinate of the cursor 44 from the reference cursor Z-coordinate
P.sub.CZ,REF, due to the non-planarirty of the shape of the surface
of the display screen 14. Also in accordance with Equation (2C),
A.sub.Z governs motion of the cursor 44 in an "apparent depth"
(i.e., along the Z axis). Since, the cursor 44 cannot physically
move away from the display screen 14, the motion of the cursor 44
in the depth direction is apparent, rather than real, in light of
the ability of human vision to perceive depth in relation to a
visual image that appears on the display screen 14. The scale
factors A.sub.X, A.sub.Y, and A.sub.Z may be constants that have
been determined prior to the calculation of P.sub.C via Equation
(2A), (2B), and (2C). Alternatively, A.sub.X, A.sub.Y, and A.sub.Z
may be spatially dependent in order to simulate scaling that varies
with spatial location of the cursor 44.
[0042] As a first example, a scale factor A.sub.X of 0.5 cm/inch
denotes that the cursor 44 moves 0.5 cm in the X direction per inch
of movement of the acoustic source 22 (and thus also the pointing
device 20) in the X direction. As a second example, a scale factor
A.sub.X of 0.1 inch/inch denotes that the cursor 44 moves 0.1
inches in the X direction per inch of movement of the acoustic
source 22 (and thus also the pointing device 20) in the X
direction. As a third example, a scale factor A.sub.X of 600
pixels/inch denotes that the cursor 44 moves 600 pixels in the X
direction per inch of movement of the acoustic source 22 (and thus
also the pointing device 20) in the X direction. The preceding
examples also apply analogously for A.sub.Y and A.sub.Z in relation
to motion in the Y and Z directions, respectively, while
recognizing that the depth motion of the cursor 44 in the Z
direction is apparent motion rather than real motion.
[0043] The case of A.sub.Z=0 restricts all motion (i.e., real and
apparent motion) of the cursor 44 to the surface of the display
screen 14, with no motion in the depth direction (i.e., behind the
display screen 14). Thus if A.sub.Z=0, any motion of the acoustic
source 22 (and thus also the pointing device 20) in the Z direction
(or the -Z direction) will have no effect on the position of the
cursor 44 on the display screen 14. In order for the cursor 44 to
have apparent motion away or toward the display screen 14, the
condition A.sub.Z.noteq.0 must be satisfied.
[0044] The acoustic source 22 could generate the acoustic signal 28
at any acoustic frequencies. It is beneficial, however, for the
acoustic source 22 to generate the acoustic signal 28 at
frequencies above those frequencies that can be heard by a human
being (i.e., above about 20 kHz). Additionally, the phase-shift
time delay period .DELTA.T.sub.ij (defined supra) should be less
than the period T of the acoustic signal 28 so that .DELTA.T.sub.ij
could be unambiguously calculated from comparison of the electrical
signals S.sub.1 and S.sub.j (for j=2, 3, and 4). It is noted that
sound travels in air at room temperature at a speed (C) of about
1100 ft/sec, so that a value of 1 ft for
(.vertline.P.sub.1-P.sub.0.vertline.-.vertline.P.sub.1-P.sub.0.vertline.
has an associated phase-shift time delay period .DELTA.T.sub.12 of
less than 1 msec (see Equation (1)). Since a frequency of 20 kHz
has a period of 50 microseconds, the acoustic signal 28 should
include at least two discrete frequencies. For example, a composite
signal of two frequencies, whose periods are 47 microseconds and 49
microseconds, would have a period of about 2.3 msec. As another
example, a composite signal of three frequencies, whose periods are
43 microseconds, 47 microseconds, and 49 microseconds, would have a
period of about 99 msec. Thus, at frequencies of at least about 20
kHz, the acoustic signal 28 should have at least two frequency
components. At frequencies of at least about 20 kHz with the
acoustic signal 28 having at least three frequency components, the
present invention would benefit from having the period T of the
acoustic signal 28 substantially larger than the phase-shift time
delay periods .DELTA.T.sub.ij (i=1, 2, 3 and j=1, 2, 3 and
i.noteq.j).
[0045] If the microphones M.sub.1, M.sub.2, M.sub.3, and M.sub.4
are able to detect a range of acoustic frequencies, then the
microphones M.sub.1, M.sub.2, M.sub.3, and M.sub.4 could
potentially detect frequencies other than those frequencies present
in the acoustic signal 28, which may cause erroneous calculations
of the phase-shift time delay periods .DELTA.T.sub.ij (i=1, 2, 3
and j=1, 2, 3 and i.noteq.j). Accordingly, filters F.sub.1,
F.sub.2, F.sub.3, and F.sub.4 (see FIG. 1) may be used to filter
the electrical signals S.sub.1, S.sub.2, S.sub.3, and S.sub.4,
respectively, so as to remove from S.sub.1, S.sub.2, S.sub.3, and
S.sub.4 all frequency components except those frequency components
present in the acoustic signal 28.
[0046] Although the embodiments described herein disclose four
microphones, namely M.sub.1, M.sub.2, M.sub.3, and M.sub.4, the
scope of the present invention includes N such microphones such
that N.gtoreq.4. If N>4 then the extra N-4 microphones could be
used to, inter alia, infer more than one value of the position
P.sub.0 of the pointer device. Said multiple computed values of
P.sub.0 could be averaged to such that the resulting average value
of P.sub.0 has improved statistical accuracy as compared with
P.sub.0 that would be inferred from exactly four microphones.
[0047] While embodiments of the present invention have been
described herein for purposes of illustration, many modifications
and changes will become apparent to those skilled in the art.
Accordingly, the appended claims are intended to encompass all such
modifications and changes as fall within the true spirit and scope
of this invention.
* * * * *